Chemical Supply System

ABSTRACT

A chemical supply system comprises, as principal elements, a chemical storage tank in which a liquid chemical for cleaning is stored in the state of its formulated concentrate, a chemical supply apparatus connected to the chemical storage tank for positively performing chemical supply, a piping system connected to the chemical supply apparatus to form a supply flow passage that is a passage for ultrapure water which the liquid chemical is to be mixed with, a pair of discharge nozzles disposed at end portions of the piping system so as to oppose surfaces of a wafer set in a cleaning chamber to supply a cleaning liquid onto the surfaces. Thereby, remarkable miniaturization/simplification of a cleaning liquid supply system including chemical tanks is intended, it is made possible easily and rapidly to compound and supply a cleaning liquid at an accurate chemical concentration, and particles or the like being generated and mixing in a cleaning liquid, are suppressed to the extremity.

This application is a divisional application of application Ser. No.10/849,836, filed May 21, 2004, which is a divisional application ofapplication Ser. No. 09/436,637, filed Nov. 9, 1999, now U.S. Pat. No.6,764,212, which claims priority to JP 10-319035, filed Nov. 10, 1998;JP 11-7063, filed Jan. 13, 1999; and JP 11-316244, filed Nov. 8, 1999.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a chemical supply pump, a chemicalsupply apparatus, and a chemical supply system (a chemical supplymethod) for accurately supplying a desired quantity of a liquidchemical, in particular, it is suitable for applying to a substratecleaning apparatus (a substrate cleaning method) for cleaningsemiconductor wafers or the like.

2. Description of the Related Art

Conventionally in a semiconductor wet process, used is a substratecleaning apparatus for performing a process such as cleaning with acleaning liquid of ultrapure water and a liquid chemical. As such asubstrate cleaning apparatus, remarked is a substrate single wafer spincleaning apparatus in which substrates are loaded one by one and acleaning liquid is supplied with rotating the substrate in acircumferential direction.

In a conventional substrate cleaning apparatus, it was indispensable toprovide a plurality of large-sized cleaning liquid storage tanks forpreparing various liquid chemicals at desired concentrations necessaryfor cleaning. Accordingly, the whole system becomes a very large scaleand complex inevitably in this case.

Besides, due to the necessity of providing a plurality of cleaningliquid storage tanks according to the necessary kinds of cleaningliquids as described above, particles are easy to mix in when a cleaningliquid is compounded. Further, generation of particles and (metal)contamination from various liquid-contact portion caused by complicationof the substrate cleaning apparatus is in question.

In this manner, at present, it is difficult to avoid increases in scaleand complication of the whole apparatus attendant upon an increase incleaning speed of substrate cleaning apparatus. It is the present statethat establishment of a technique of preventing particle-mixing or thelike in a cleaning liquid, is eagerly desired.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a chemical supplypump, a chemical supply apparatus, a chemical supply system, a substratecleaning apparatus, a chemical supply method, and a substrate cleaningmethod, wherein remarkable miniaturization/simplification of a cleaningliquid supply system including chemical reservoirs (chemical storagetanks) is intended, it becomes possible easily and rapidly to compoundand supply a cleaning liquid at an accurate chemical concentration whenit is required in cleaning, and it is realized to suppress particles orthe like being generated and mixing in a cleaning liquid, to theextremity.

In order to attain the above object, a chemical supply pump of thepresent invention is a chemical supply pump in which a flow passage forpassing a predetermined liquid chemical is formed, a suction valve whichis closed by pressure rise of said liquid chemical is provided at aflowing-in port of said flow passage, and a discharge valve which isclosed by pressure fall of said liquid chemical is provided at aflowing-out port of said flow passage, wherein at least part of a liquidcontact surface in said flow passage is made of a compact member withnon-permeability and a high anti-corrosion property to said liquidchemical, and part of said compact member is made into a movable wall,and a shaker connected to said movable wall is provided, and saidmovable wall is oscillated in a direction substantially perpendicular toits wall surface by drive of said shaker to change the volume of saidflow passage periodically.

A chemical supply apparatus of the present invention comprises achemical supply pump, and a connecting flow passage connecting a supplyflow passage that is a passage for a solvent with which said liquidchemical is mixed, and said chemical supply pump, wherein a tubulemember directly connecting said supply flow passage is provided in saidconnecting flow passage. In said chemical supply pump, a flow passagefor passing a predetermined liquid chemical is formed, a suction valvewhich is closed by pressure rise of said liquid chemical is provided ata flowing-in port of said flow passage, and a discharge valve which isclosed by pressure fall of said liquid chemical is provided at aflowing-out port of said flow passage, at least part of a liquid contactsurface in said flow passage is made of a compact member withnon-permeability and a high anti-corrosion property to said liquidchemical, and part of said compact member is made into a movable wall,and a shaker connected to said movable wall is provided, and saidmovable wall is oscillated in a direction substantially perpendicular toits wall surface by drive of said shaker to change the volume of saidflow passage periodically. Said chemical supply apparatus dischargessaid liquid chemical from said tubule member into said solvent passingthrough said supply flow passage by drive of said chemical supply pumpto compound a mixture solution at a desired concentration.

A chemical supply system of the present invention is a chemical supplysystem comprising at least one kind of chemical reservoir easy to move,a chemical supply apparatus connected in correspondence to said chemicalreservoir, and said supply flow passage. Said chemical supply apparatuscomprises a chemical supply pump, and a connecting flow passageconnecting the supply flow passage that is a passage for a solvent withwhich said liquid chemical is mixed, and said chemical supply pump,wherein a tubule member directly connected to said supply flow passageis provided in said connecting flow passage. In said chemical supplypump, a flow passage for passing a predetermined liquid chemical isformed, a suction valve which is closed by pressure rise of said liquidchemical is provided at a flowing-in port of said flow passage, and adischarge valve which is closed by pressure fall of said liquid chemicalis provided at a flowing-out port of said flow passage, at least part ofa liquid contact surface in said flow passage is made of a compactmember with non-permeability and a high anti-corrosion property to saidliquid chemical, and part of said compact member is made into a movablewall, and a shaker connected to said movable wall is provided, and saidmovable wall is oscillated in a direction substantially perpendicular toits wall surface by drive of said shaker to change the volume of saidflow passage periodically. Said chemical supply apparatus dischargessaid liquid chemical from said tubule member into said solvent passingthrough said supply flow passage by drive of said chemical supply pumpto compound a mixture solution at a desired concentration. Said chemicalsupply system discharges said mixture solution made into thepredetermined concentration from a discharge portion provided at an endportion of said supply flow passage, by drive of said chemical supplypump of said chemical supply apparatus.

A substrate cleaning apparatus of the present invention is a substratecleaning apparatus in which a cleaning liquid is supplied to a setsubstrate to clean, and comprises a chemical supply system. Saidchemical supply system comprises at least one kind of chemical reservoireasy to move, a chemical supply apparatus connected in correspondence tosaid chemical reservoir, and a supply flow passage. Said chemical supplyapparatus discharges said liquid chemical from said tubule member intosaid solvent passing through said supply flow passage by drive of saidchemical supply pump to compound a mixture solution at a desiredconcentration, and comprises a chemical supply pump, and a connectingflow passage connecting the supply flow passage that is a passage for asolvent with which said liquid chemical is mixed, and said chemicalsupply pump, wherein a tubule member directly connected to said supplyflow passage is provided in said connecting flow passage. In saidchemical supply pump, a flow passage for passing a predetermined liquidchemical is formed, a suction valve which is closed by pressure rise ofsaid liquid chemical is provided at a flowing—in port of said flowpassage, and a discharge valve which is closed by pressure fall of saidliquid chemical is provided at a flowing-out port of said flow passage,at least part of a liquid contact surface in said flow passage is madeof a compact member with non-permeability and a high anti-corrosionproperty to said liquid chemical, and part of said compact member ismade into a movable wall, and a shaker connected to said movable wall isprovided, and said movable wall is oscillated in a directionsubstantially perpendicular to its wall surface by drive of said shakerto change the volume of said flow passage periodically. Said substratecleaning apparatus uses said mixture solution as said cleaning liquid.

A chemical supply method of the present invention is a chemical supplymethod using a chemical supply pump, wherein, in said chemical supplypump, a flow passage for passing a predetermined liquid chemical isformed, a suction valve which is closed by pressure rise of said liquidchemical is provided at a flowing-in port of said flow passage, and adischarge valve which is closed by pressure fall of said liquid chemicalis provided at a flowing-out port of said flow passage, at least part ofa liquid contact surface in said flow passage is made of a compactmember with non-permeability and a high anti-corrosion property to saidliquid chemical, and part of said compact member is made into a movablewall, and a shaker connected to said movable wall is provided, and saidmovable wall is oscillated in a direction substantially perpendicular toits wall surface by drive of said shaker to change the volume of saidflow passage periodically, and said chemical supply pump is driven, andsaid liquid chemical is discharged into a solvent passing through saidsupply flow passage to compound a mixture solution at a desiredconcentration.

A substrate cleaning method of the present invention is a substratecleaning method in which a cleaning liquid is supplied to a setsubstrate to clean, wherein a chemical supply pump is used in which aflow passage for passing a predetermined liquid chemical is formed, asuction valve which is closed by pressure rise of said liquid chemicalis provided at a flowing-in port of said flow passage, and a dischargevalve which is closed by pressure fall of said liquid chemical isprovided at a flowing-out port of said flow passage, at least part of aliquid contact surface in said flow passage is made of a compact memberwith non-permeability and a high anti-corrosion property to said liquidchemical, and part of said compact member is made into a movable wall,and a shaker connected to said movable wall is provided, and saidmovable wall is oscillated in a direction substantially perpendicular toits wall surface by drive of said shaker to change the volume of saidflow passage periodically, and said chemical supply pump is driven, saidliquid chemical is discharged into a solvent passing through said supplyflow passage, a mixture solution at a desired concentration iscompounded, and said mixture solution is used as said cleaning liquid toclean said substrate surface.

A chemical supply system of the present invention is a chemical supplysystem for supplying a mixture solution in which a liquid chemical ismixed and diluted with a solvent, comprising at least one kind ofchemical reservoir easy to move, in which said liquid chemical at a highconcentration is stored, a chemical supply means for sucking apredetermined quantity of said liquid chemical from said chemicalreservoir and feeding out it, and a piping system forming a flow passagefor said solvent connected to said chemical supply means, and having adischarge portion for said solution at an end portion, wherein, at thetime of use, a necessary quantity of said liquid chemical is mixed withsaid solution flowing in said piping system, said mixture solution at adesired concentration is produced, and said mixture solution is suppliedfrom said discharge portion.

According to a chemical supply pump of the present invention, a movablewall is driven and controlled by a shaker to oscillate, and a liquidchemical is discharged by the pressure, and a desired quantity of theliquid chemical can be discharged and supplied with accuracy. Here, usedis a compact member, preferably, amorphous carbon, that at least part ofthe liquid contact surface has non-permeability and a highanti-corrosion property to the liquid chemical. This amorphous carbon isa material easy to control its porosity, and one whose porosity issubstantially zero is very superior in non-permeability and the highanti-corrosion property. Accordingly, by providing this amorphous carbonon the important portion of the liquid contact surface, the supplyquantity control of the liquid chemical becomes more accurate, andmixing of particles or the like into the liquid chemical is suppressed.

Further in the present invention, provided is a chemical supplyapparatus including this chemical supply pump as a component. Thischemical supply apparatus mixes a liquid chemical from a tubule memberwith a solvent whose representative is ultrapure water passing through asupply flow passage by drive of the chemical supply pump, and mixturesolutions at various concentrations can easily be compounded at need.Here, in case that the discharge direction of the liquid chemical is adirection substantially perpendicular to the flow direction of the abovesolvent, by applying a pressure to the liquid chemical such that thelinear velocity of the liquid chemical discharged from the tubule memberis sufficiently greater than the linear velocity of the solvent passingthrough the supply flow passage, the liquid chemical reaches theopposite wall surface of the supply flow passage in the solvent, and amixture solution at a uniform concentration is compounded in a moment.

Further in the present invention, provided is a chemical supply systemincluding this chemical supply apparatus as a component and forsupplying the above mixture solution. In this chemical supply system,because it is possible to produce mixture solutions at desiredconcentrations at need as described above, enough is the easily movablesmall-sized reservoir for the liquid chemical that is the formulatedconcentrate. That is, in this chemical supply system, there is nonecessity of providing very large reservoirs for mixture solutionsdifferent in chemical concentration and kind as conventionally, and notonly particle mixing to a cleaning liquid, or the like, can besuppressed, but also remarkable reduction/simplification of the scale ofthe whole system can be realized. Accordingly, by applying this chemicalsupply system to, e.g., a substrate cleaning apparatus, it becomespossible rapidly and easily to supply various pure cleaning liquids(mixture solutions) different in concentration and kind.

Accordingly, according to the present invention, remarkableminiaturization/simplification of a cleaning liquid supply systemincluding chemical reservoirs (chemical storage tanks) is intended, itbecomes possible easily and rapidly to compound and supply a cleaningliquid at an accurate chemical concentration when it is required incleaning, and it is realized to suppress particles or the like beinggenerated and mixing in a cleaning liquid, to the extremity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a typical view showing an example of wafer one-by-one (singlewafer) spin cleaning apparatus including a chemical supply systemaccording to the first example;

FIG. 2 is a schematic sectional view showing an example of cleaningchamber that is a component of the single wafer spin cleaning apparatusaccording to the first example;

FIG. 3 is a schematic front view showing a chemical supply pump that isa component of the chemical supply system;

FIG. 4 is a schematic sectional view taken along line 4-4 in FIG. 3;

FIG. 5 is a schematic sectional view taken along line 5-5 in FIG. 3;

FIG. 6 is a schematic sectional view taken along one-dot chain line 6-6in FIG. 3;

FIG. 7 is a schematic sectional view showing a vicinity of a flowpassage of the chemical supply pump that is a component of the chemicalsupply system;

FIGS. 8A and 8B are schematic sectional views showing a movable wallthat is a component of the chemical supply pump;

FIG. 9 is a schematic sectional view showing another suitable example ofmovable wall;

FIGS. 10A and 10B are schematic perspective views showing auxiliarymembers of the movable wall;

FIGS. 11A and 11B are schematic sectional views showing a drivetransmission means that is a component of the chemical supply pump, anda state of reaction on the movable member;

FIG. 12 is a schematic sectional view showing a vicinity of the flowpassage when the chemical supply pump drives;

FIGS. 13A through 13E are typical views showing chemical diffusionpatterns at a mixing point of a liquid chemical and ultrapure water;

FIG. 14 is a typical view showing a case of providing a plurality ofchemical supply apparatus;

FIG. 15 is a typical view showing a concrete example of mixingprevention system for particles or the like;

FIG. 16 is a typical view showing another concrete example of mixingprevention system for particles or the like;

FIG. 17 is a typical view showing still another concrete example ofmixing prevention system for particles or the like;

FIG. 18 is a typical view showing a concrete example of bubble/breakingdown detection system;

FIGS. 19A to 19C are characteristic graphs showing monitoringelectrostatic capacity by the bubble/damage detection system;

FIGS. 20A to 20C are typical views showing another concrete example ofbubble/breaking down detection system;

FIG. 21 is a typical view showing a concrete example of cleaning liquidconcentration regulation system;

FIGS. 22A to 22C are schematic sectional views showing an example ofchemical mixing system;

FIGS. 23A and 23B are schematic sectional views showing another exampleof chemical mixing system;

FIGS. 24A and 24B are schematic sectional views showing still anotherexample of chemical mixing system;

FIGS. 25A and 25B are schematic sectional views showing still anotherexample of chemical mixing system;

FIG. 26 is a schematic sectional view showing an enlarged tip endportion of the chemical mixing system of FIGS. 25A and 25B;

FIG. 27 is a typical view showing a chemical quantity regulation system;

FIG. 28 is a typical view showing a liquid surface regulation means;

FIG. 29 is a typical view for illustrating the operation principle ofthe liquid surface regulation means;

FIG. 30 is a characteristic graph showing a relation between the liquidsurface level of a cleaning liquid and capacity;

FIGS. 31A and 31B are characteristic graphs showing oscillation statesof discharge/suck by a chemical supply pump;

FIG. 32 is a characteristic graph showing relations between temperatureand quantity of dissolved air in water, nitrogen, and oxygen thinkableas dissolved gas;

FIG. 33 is a schematic sectional view showing state that a cooling meansis provided in a chemical supply pump;

FIGS. 34A and 34B are typical views showing a membranous tube that is acomponent of a degassing module; and

FIG. 35 is a schematic sectional view showing the whole construction ofa substrate cleaning apparatus of the second example.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, various concrete examples of substrate cleaning apparatusof the present invention will be described in detail with reference todrawings.

First Example

A substrate cleaning apparatus of this example is in which wafers areloaded one by one and a cleaning liquid is supplied with rotating thewafer in a circumferential direction, and a single wafer spin cleaningapparatus capable of realizing wide-ranging functions in a wet cleaningprocess for semiconductor wafers or the like.

FIG. 1 is a schematic sectional view showing the whole construction ofthe substrate cleaning apparatus of this example.

This substrate cleaning apparatus is constructed by comprising acleaning chamber 1 in which a substrate (wafer) 11 is set and cleaningis performed, and a chemical supply system 2 for producing and supplyinga cleaning liquid at a desired chemical concentration.

As shown in FIG. 2, the cleaning chamber 1 defines a closed spacewherein the wafer 11 to be cleaned is received, and is provided with agate valve 12 that is a taking in/out portion for the wafer 11. Thiscleaning chamber 1 is constructed by comprising a wafer set means 14having a wafer support pin 13 for supporting the wafer 11 at its sidesurface, and provided with a rotational drive motor for rotating thefixed wafer 11 in the direction of an arrow in FIG. 2, and a cleaningliquid collision buffer plate 15 disposed to enclose the wafer set means14 from the side. Here, the cleaning liquid collision buffer plate 15 isnot always necessary. By making the shape of the cleaning chamber have aslightly curved surface, the function of the cleaning liquid collisionbuffer plate 15 can be replaced.

In the cleaning chamber 1, provided is a nozzle (not shown) forsupplying N₂ gas, an inert gas, or the like. It is possible to dry thewafer 11 by the manner of rotating it at a high speed with blowing N₂gas or the like against the front surface or both the front and backsurfaces of the wafer 11 when the wafer 11 is dried after cleaning; toperform cleaning of the wafer 11 in the state that the interior of thecleaning chamber 1 is replaced by N₂ gas, an inert gas, or the like, ata high concentration; and so on.

The chemical supply system 2 is constructed by comprising a chemicalstorage tank 21 in which a liquid chemical for cleaning is stored in thestate of its formulated concentrate, a chemical supply apparatus 22connected to the chemical storage tank 21 for positively performingchemical supply, a piping system 23 connected to the chemical supplyapparatus 22 to form a supply flow passage that is a passage forultrapure water which the liquid chemical is to be mixed with, a pair ofdischarge nozzles 24 and 25 disposed at end portions of the pipingsystem 23 so as to oppose the surfaces of the wafer 11 set in thecleaning chamber 1 to supply a cleaning liquid onto the surfaces, and acontrol system 26 for regulating various conditions such as theconcentration and flow rate of the cleaning liquid supplied from thedischarge nozzles 24 and 25.

The chemical storage tank 21 stores a liquid chemical in the state ofits formulated concentrate at a high concentration, here, e.g., hydrogenfluoride (HF), and has a small size easy to move for taking in/out orthe like. There is also a case of providing a plurality of chemicalstorage tanks 21 according to the kinds or the like of liquid chemicals.

The chemical supply apparatus 22 is constructed by comprising a chemicalsupply pump 31 that is a diaphragm pump performing actions of feedingout a liquid chemical in an oscillation manner from the chemical storagetank 21 by utilizing piezoelectric effect, a connecting pipe 32 whichconnects the piping system 23 and the chemical supply pump 31 to form aconnecting flow passage, a tubule member (capillary) 33 in theconnecting pipe 32 for directly connecting to the supply flow passage ofthe piping system 23.

As shown in FIGS. 3 to 6 and FIG. 7, in the chemical supply pump 31, aflow passage 41 for passing the liquid chemical is formed. A suctionvalve 42 which is closed due to pressure rise of the liquid chemical isprovided at the inlet port of this flow passage 41, and a dischargevalve 43 which is closed due to pressure fall of the liquid chemical isprovided at the outlet port of the flow passage 41. Here, a pair ofopposing side walls 44 and 45 constituting part of a liquid contactsurface in the flow passage 41 is made of a compact member withnon-permeability and a high anti-corrosion property to the liquidchemical, here, amorphous carbon that is a conductive member, as theprincipal material, and the side wall 44 is made into a movable wall. Asthe above compact member, ceramics or sapphire may be used instead ofamorphous carbon.

And, this chemical supply pump 31 is constructed by comprising apiezoelectric oscillator 46 that is a shaker connected to this side wall(movable wall) 44 for oscillating the movable wall 44 in directionssubstantially perpendicular to its wall surface to change the volume ofthe flow passage 41 periodically, a drive transmission means 47 disposedbetween the movable wall 44 and the piezoelectric oscillator 46 fortransmitting the oscillation from the piezoelectric oscillator 46, andsprings 48 that are means that it is considered that the piezoelectricoscillator 46 can generate no pressure in its shrinkage direction, forelastically biasing the drive transmission means 47.

Amorphous carbon that is the principal material of the side walls 44 and45, has non-permeability and a high anti-corrosion property as describedabove, and has the nature that it does not receive any contamination inrelation to the liquid chemical used for cleaning the wafer 11, inparticular, oxidizing agent such as hydrogen fluoride, a hydrogenperoxide solution, and ozone. As amorphous carbon used here, uniformamorphous carbon, fibrous amorphous carbon, or a complex material ofboth is preferable. Uniform amorphous carbon is a material having acompact isotropic structure without pores and superior in gas barrierand liquid interception properties, and is possible to control theporosity in accordance with the application. Fibrous amorphous carbon isa carbon porous body having a three-dimensional skeletal structure, andporous carbon having uniformity of pores.

Here, experimental examples in which non-permeability/highanti-corrosion property of amorphous carbon were examined, will bedescribed. In this experiment, a supply line from the fluoric acidformulated concentrate to a dilute fluoric acid preparation system wasconstructed using amorphous carbon piping (the outside diameter of about6 mm and the inside diameter of about 4 mm) with the porosity of 0%, andthe elution degrees of various metals in case of repetitive use wereexamined. The following table shows the experimental results.

eluted ingredient Al Ca Mg Na Fe Ni Cr Ti eluted ingredientconcentration <1 <1 <1 <1 <1 <1 <1 <1 one week after eluted ingredientconcentration <1 <1 <1 <1 <1 <1 <1 <1 one month after Sample area: 40 ×10 × 2 (mm) HF50% quantity used: 1 (kg)

Even when long use over one month is repeated in this manner, it isfound that any eluted ingredient is not given to the fluoric acidformulated concentrate at a high concentration (HF 50%). Accordingly,preparation of highly pure dilute fluoric acid becomes possible by usingthis amorphous carbon.

In a conventional chemical supply system constructed with a fluororesin,because diffusion of HF molecules in the fluororesin is inevitable,there is the defect that slight HF diffusion can not be suppressed in along term. As this example, by applying amorphous carbon to a liquidcontact portion, this problem can be solved.

The movable wall 44 functions as a diaphragm, and has a shape thatbecomes thicker from the center to the periphery, as shown in FIG. 8B.This shape is the optimum shape for dispersing the mechanical stressacting on one portion in consideration of reinforcement of the vicinityof the periphery that is the fixture portion, in addition to that theportion that the pressure received by the movable wall 44 becomes themaximum is near the center, and here becomes the portion deformingrepeatedly in particular. As shown in FIG. 8A, in case that the movablewall 44 has a uniform thickness for example, the mechanical stress isconcentrated near the center and the durability may be detracted. Asshown in FIG. 9, it is also suitable that the movable wall 44 is formedso as to become thicker from the center to the periphery and have asectional shape laterally symmetrical in the drawing.

Further, as shown in FIGS. 10A and 10B, between the movable wall 44 andthe drive transmission means 47, provided is an auxiliary member 51 foruniformly transmitting the pressure from the drive transmission means 47to the movable wall 44 to disperse the mechanical stress. As a concreteexample of this auxiliary member 51, preferable is a concentric O-ringgroup 51 a made of rubber or an elastic adhesive and having a shapeaccording to the pressure, as shown in FIG. 10A, a sheet 51 b producingthe same effect as the O-ring group 51 a, as shown in FIG. 10B, or thelike.

The drive transmission means 47 is made of SUS, in which, inanticipation of reaction received from the liquid chemical when thedirect oscillation transmission portion (near the center) to the movablewall 44 is pressed, the portions near the center and where the abovereaction is great are formed to be thicker, as shown in FIG. 11A. Thatis, as shown in FIG. 11B, when the maximum pressure acts on the vicinityof the center of the movable wall 44, the reaction from the liquidchemical in the flow passage 41 becomes the maximum near the peripheryof the movable wall 44. So, if the drive transmission means 47 is formedinto a shape that the thickness of the peripheral vicinity 47 bsuccessive to the central vicinity 47 a is great as shown in the drawingin anticipation of this reaction, the pressure acting on the movablewall 44 becomes substantially uniform on the whole. In this case, forsuppressing the deformation of the auxiliary member 51 due to a verticalforce in FIG. 11A, as small as possible, it is preferable to make cutsor the like in the auxiliary member 51.

The operation of this chemical supply pump 31 is as follows. When themovable wall 44 that is a diaphragm moves rightward in FIG. 7, the flowpassage 41 becomes at a negative pressure and the discharge valve 43becomes the closed state. When it moves leftward as shown in FIG. 12,the flow passage 41 becomes at a positive pressure and the suction valve42 becomes the closed state, and the discharge valve 43 becomes the openstate to discharge the liquid chemical. Here, it is preferable tocontrol the oscillation frequency of the movable wall 44 by drive of thepiezoelectric oscillator 46, in the degree of 20 Hz for example, and itis suitable that the discharge pressure of the liquid chemical is 1.5kg/cm² or more for example.

The capillary 33 that is a tubule member is made of amorphous carbonsimilar to the side walls 44 and 45 as the principal material, and thetube diameter is, e.g., in the degree of Φ0.2 mm, and the dischargequantity is, e.g., 0.3 cc/sec. By oscillation drive of the chemicalsupply pump 31, the liquid chemical is discharged from this capillary 33into ultrapure water in the piping system 23.

The piping system 23 forms a supply flow passage for ultrapure water asdescribed above, and the tube diameter is, e.g., in the degree of 5 mm,and the flow rate is, e.g., in the degree of 3.4 l/min. In this pipingsystem 23, provided are a flow rate regulation means 34 for regulatingthe flow rate of ultrapure water passing through the piping system 23, aconcentration regulation means 35 for regulating the concentration ofthe cleaning liquid passing through the piping system 23, and a mixingmeans 36 disposed at the connecting portion to the capillary 33 of thepiping system 23 for producing a rotational flow in the cleaning liquidto stir and uniformize the cleaning liquid. These flow rate regulationmeans 34, concentration regulation means 35, and mixing means 36 will bedescribed later in detail. The discharge conditions of the liquidchemical into the piping system 23 are as follows.

In general, a flow that the passage quantity per unit time is constanteven in any section of a fluid passing through a tube, is calledconstant flow. In constant flow, there are two forms of laminar flow andturbulent flow. Laminar flow is a flow that the flow axis keeps a linearshape in relation to the flow passage axis, and the flow rate isrelatively small. on the other hand, turbulent flow is a flow that theflow axis becomes a state of irregularly whirling, and the flow rate isrelatively great. It is known that conditions for appearance of laminarflow and turbulent flow are classified by so-called Reynolds number. Incase of the Reynolds number of 2000 or less, even when the flow axis isdisturbed by adding stirring, the downstream returns to laminar flow.The range of the Reynolds number of 2300 to 3000 is considered theboundary (critical Reynolds number) between laminar flow and turbulentflow.

Here, when the Reynolds number is R (no dimension), the inside diameterof the tube is D (cm), the linear velocity of the liquid is u (cm/sec),the dynamic viscosity of the liquid is ν (cm²/sec), the viscosity of theliquid is η (dyn·sec), and the density of the liquid is ρ (g/cm³), theReynolds number R is expressed by:

$\begin{matrix}{R = {D \cdot {u/v}}} \\{= {D \cdot u \cdot {\rho/{\eta.}}}}\end{matrix}$

FIGS. 13A through 13E are typical views showing chemical diffusionpatterns at a mixing point P of a liquid chemical and ultrapure water inthis example.

First, as a comparative example, a chemical diffusion pattern when theconnecting tube 32 is directly connected to the piping system 23 withoutusing the capillary 33, is shown in FIG. 13A and FIG. 13B. In this case,because the linear velocity of ultrapure water is larger than the linearvelocity of the liquid chemical, laminar flow of ultrapure water is notdisturbed and the liquid chemical is transported along the tube wall asit is in the non-diffusion state.

In comparison with that, in case of this example, as shown in FIGS.13C-13E, by selecting the capillary 33, by applying a pressure at whichthe linear velocity of the liquid chemical discharged from the capillary33 is sufficiently larger than the linear velocity of ultrapure water(for example, the pressure at which it is injected at the flow velocityabout ten times of the flow velocity of ultrapure water), to the liquidchemical by the chemical supply pump 31, the liquid chemical reaches theopposite wall surface of the piping system 23 in ultrapure water. Thechemical diffusion pattern at this time has a shape elongated in theflowing-out direction by laminar flow in viewing from the side, a shapesuch that the tip end of the chemical flow is bent by collision againstthe opposite wall surface, in viewing from the front, and a shape thatthe tip end of the chemical flow is separated to both sides by collisionagainst the opposite wall surface and further elongated in theflowing-out direction, in viewing from the upside. That is, in thiscase, a mixture solution (cleaning liquid) of the liquid chemical andultrapure water is compounded at a uniform concentration, andtransported through the piping system 23.

The control system 26 comprises a chemical supply control means 37 forcontrolling the supply quantity of the liquid chemical to ultrapurewater of the chemical supply pump 31, and driving the flow rateregulation means 34, and a concentration control means 38 for drivingthe concentration regulation means 35. And, the chemical supply controlmeans 37 and the concentration control means 38 are connected, theresult of the concentration control by the concentration control means38 is fed back to the chemical supply control means 37 to control thechemical supply pump 31, and the supply quantity of the liquid chemicalis regulated. Control to various additional systems described later isalso made by the control system 26.

As shown in FIG. 14, there is a case that a plurality of chemical supplyapparatus 22 (three of A, B, and C in the example shown in the drawing)is provided. In this case, each chemical supply apparatus 22 arbitrarilydrives, and mixes each liquid chemical to ultrapure water passingthrough the supply flow passage of the piping system 23, in a desiredorder, and desired cleaning liquids are supplied to the wafer il surfacein order from the discharge nozzles 24 and 25.

In this manner, in the substrate cleaning apparatus of this example,first by the chemical supply pump 31, the piezoelectric oscillator 46drives and controls the movable wall 44 to oscillate, and the liquidchemical is discharged by the pressure, and a desired quantity of theliquid chemical can be discharged and supplied with accuracy. Here, usedis a compact member, preferably, amorphous carbon, that at least part ofthe liquid contact surface has non-permeability and a highanti-corrosion property to the liquid chemical. This amorphous carbon isa material easy to control its porosity, and one whose porosity issubstantially zero is very superior in non-permeability and the highanti-corrosion property. Accordingly, by providing this amorphous carbonon the important portion of the liquid contact surface, the supplyquantity control of the liquid chemical becomes more accurate, andmixing of particles or the like into the liquid chemical is suppressed.

Further in this example, provided is the chemical supply apparatus 22including this chemical supply pump 31 as a component. This chemicalsupply apparatus 22 mixes the liquid chemical from the capillary 33 withultrapure water passing through the piping system 23 by drive of thechemical supply pump 31, and mixture solutions (cleaning liquids) atvarious concentrations can easily be compounded at need. Here, in casethat the discharge direction of the liquid chemical is a directionsubstantially perpendicular to the flow direction of ultrapure water, byapplying a pressure to the liquid chemical such that the linear velocityof the liquid chemical discharged from the tubule member is sufficientlylarger than the linear velocity of ultrapure water passing through thepiping system 23, the liquid chemical reaches the opposite wall surfaceof the piping system 23 in ultrapure water, and a mixture solution at auniform concentration is compounded in a moment.

Further in this example, provided is the chemical supply system 2including the chemical supply apparatus 22 as a component and forsupplying a cleaning liquid. In this chemical supply system 2, becauseit is possible to produce cleaning liquids at desired concentrations atneed as described above, enough is the easily movable small-sizedreservoir 21 of the liquid chemical that is the formulated concentrate.That is, in this chemical supply system 2, there is no necessity ofproviding very large reservoirs for mixture solutions different inchemical concentration and kind as conventionally, and not only particlemixing to a cleaning liquid, or the like, can be suppressed, but alsoremarkable reduction/simplification of the scale of the whole system canbe realized. Accordingly, in the substrate cleaning apparatus of thisexample provided with this chemical supply system 2, it becomes possiblerapidly and easily to supply various pure cleaning liquids different inconcentration and kind.

In the substrate cleaning apparatus of this example, in order to ensurethe further suppression of particle generation or the like and theaccuracy of the chemical concentration of the cleaning liquid, variousadditional systems as shown hereinafter are provided to the chemicalsupply system constructed as described above.

First, a mixing prevention system (chemical discharge stop means) 39 ofremaining chemical when chemical injection to ultrapure water in thepiping system 23 is stopped, will be described.

FIG. 15 is a typical view showing a concrete example of the mixingprevention system 39. Here, exemplified is a so-called suck-back devicehaving an electric heating system. This suck-back device 61 is made ofamorphous carbon as the principal material, and provided so as to coverpart of the connecting tube 32. An electric power source 62 synchronouswith drive/stop of the chemical supply pump 31 is connected to thissuck-back device 61, and the liquid chemical near the suck-back device61 is heated to a predetermined temperature by the heat transfer systemof the suck-back device 61 in the state of the power source 62 being ONwhen the liquid chemical is supplied. When the chemical supply pump 31is stopped, although the power source 62 becomes OFF synchronously withthat, since the pressure produced due to flowing of ultrapure watercloses the discharge valve 43 of the chemical supply pump 31 through thecapillary 33, the liquid chemical slightly contracts due to naturalcooling, and with that, some quantity of ultrapure water in the pipingsystem 23 is sucked from the capillary 33 to the chemical supply pump 31side. Thereby, the interior of at least a portion in the capillary 33 indirect contact with ultrapure water in the piping system 23 is replacedby ultrapure water, and the liquid chemical is completely interceptedfrom ultrapure water in the piping system 23.

Besides, a suck-back device having a compression system may be usedinstead of the suck-back device 61. In this case, for example, asolenoid is formed by winding on the suck-back device made of a plastic,and it is constructed such that a current to the solenoid is made OFFsynchronously with stop of the chemical supply pump 31. In general, thesolenoid slightly expands radially by OFF of the current, and therebysome quantity of ultrapure water is sucked from the capillary 33.

Besides, utilizing that the capillary 33 has electrical conductivity, anelectric heater 63 synchronous with drive/stop of the chemical supplypump 31 may be provided to the capillary 33, as shown in FIG. 16. Inthis case, like the function of the above suck-back device 61, when theelectric heater power source 63 is made OFF synchronously with stop ofthe chemical supply pump 31, the liquid chemical slightly contracts dueto natural cooling, and with that, some quantity of the liquid chemicalis sucked from the capillary 33 and completely intercepted fromultrapure water in the piping system 23. This mixing prevention systemusing the capillary 33 is suitable even when it is used together withthe above suck-back device.

Besides, as shown in FIG. 17, a mixing prevention system 39 may beconstructed by having a connecting tube 52 connected directly to part ofthe connecting tube 32 in the vicinity of the capillary 33 and connectedto the portion corresponding to the upstream of ultrapure water of theconnecting portion of the capillary 33 of the piping system 23, andproviding a capillary 40 that is another tubule member connecteddirectly to that portion of the piping system 23 in the connecting tube52. In this case, the mixing prevention system 39 operates such that thevalve 53 is opened synchronously with stop of the chemical supply pump31, ultrapure water is supplied from the capillary 40 into theconnecting tube 32, and remaining liquid chemical in the connecting tube32 is pushed out to the piping system 23 side. At this time, because thecheck valve 54 provided integrally with the chemical supply pump 31(only the check valve 54 is shown in FIG. 17 for convenience' sake) ispresent, the remaining liquid chemical does not flow to the chemicalsupply pump 31 side, and flows to the capillary 33 side. Thereby, theremaining liquid chemical is pushed out to the piping system 23 side.And, the valve 53 is closed synchronously with operation start of thechemical supply pump 31, and by action of the check valve 55 provided inthe connecting tube 52 between the valve 53 and the capillary 40, theliquid chemical is prevented from flowing out into the connecting tube52. According to this mixing prevention system 39, remaining liquidchemical can easily and surely be prevented from being diffused in thepiping system 23.

Next, a system for detecting bubble generation in the liquid chemical inchemical supply, and damage on the movable wall 44 easiest to bebreaking down due to drive of the chemical supply pump 31, or the like,will be described.

FIG. 18 is a typical view showing a concrete example of thebubble/breaking down detection system.

In this bubble/breaking down detection system 71, utilizing that theside walls 44 and 45 of the chemical supply pump 31 have electricalconductivity, a capacitor is formed by regarding them as opposedelectrodes and using the liquid chemical in the flow passage 41 as adielectric substance, and the electrostatic capacity of this capacitoris monitored by an electrostatic capacity monitor 72 connected to theopposed electrodes. In this case, in order to ensure the certaincapacitor function of the side walls 44 and 45, it is preferable toinsert an insulating material 73 into the fixture portion (this portionis also made of amorphous carbon) of the side wall (movable wall) 44.

The detection operation by the bubble/breaking down detection system 71will be described with reference to FIGS. 19A to 19C.

First, when no bubble or no damage is generated, the electrostaticcapacity C shows a substantially constant value as shown in FIG. 19A.And, for example, when bubbles are generated in the liquid chemical inthe flow passage 41, the electrostatic capacity C falls for the time ofpassing through the flow passage 41 as shown in FIG. 19B. Besides, whenbreaking down occurs on the movable wall 44, the electrostatic capacityC falls with the time of the break being a boundary and becomes asubstantially constant state at a predetermined value as shown in FIG.19C. In this manner, by monitoring the electrostatic capacity C,generation of bubbles or break can be detected with ease.

Besides, as another example of bubble detection system, as shown in FIG.20A, there is a bubble detection system 74 constructed by comprising apair of e.g., ring-like electrodes 75 disposed on the connecting tube32, and an LCR meter 76 connected to each electrode 75. FIG. 20B beingnormalcy, when bubbles are generated in the liquid chemical passingbetween the electrodes 72 as shown in FIG. 20C, the electrostaticcapacity C falls for that time like the above. So, by monitoring theelectrostatic capacity C with the bubble detection system 74, generationof bubbles can be detected with ease like the above.

Next, a system for controlling the discharge quantity of the liquidchemical from the chemical supply pump 31 to ultrapure water, andmonitoring the flow condition of the cleaning liquid, that is, whetheror not the cleaning liquid flows normally.

FIG. 21 is a typical view showing a concrete example of the cleaningliquid flow detection system.

This cleaning liquid flow detection system 81 comprises a pair ofthermistor temperature detection terminals 82 respectively embedded inboth ends of the wall surface of the capillary 33 near the joiningportion between the capillary 33 and the piping system 23, and isconstructed such that an electric heater 83 heats the capillary 33 to apredetermined temperature synchronously with drive of the chemicalsupply pump 31.

The temperature difference between the temperature detection terminals82 is measured by this cleaning liquid flow detection system 81, andthereby a change in flow condition is detected. That is, ultrapure waterflows within the piping system 23 in the direction indicated by an arrowin FIG. 21, and a concentration inclination according to the chemicaldischarge quantity arises between the temperature detection terminals82. Because this concentration inclination is a function of temperature,by measuring the temperature difference between the temperaturedetection terminals 82, the chemical discharge quantity is detected. Inthis manner, according to the cleaning liquid flow detection system 81,it becomes possible to control the flow condition of the cleaning liquidalways in a suitable condition.

Next, a system for preventing corrosion due to the liquid chemical orvapor of the liquid chemical in the chemical supply pump 31, will bedescribed.

FIGS. 5 and 6 are typical views showing a concrete example of thecorrosion prevention system (sectional views: two directions).

In the chemical supply pump 31, thinkable is a case that the bypass 49has a portion made of a fluororesin, and a very minute gap is formedbetween the movable wall 44 and the side wall 45. In the portion with arelatively low anti-corrosion property made of such a resin or thecorner portions forming the gap, when a liquid chemical stays, forexample, if the liquid chemical is HF, vapor of the liquid chemical isapt to be generated from there, and it may become one cause of bringingabout corrosion. So, by providing the corrosion prevention system,corrosion from the liquid chemical or the chemical vapor can beprevented. This corrosion prevention system 91 is constructed bycomprising a ventilation system 92 (shown by arrows in FIGS. 5 and 6)for a carrier gas passing through the portion with a relatively lowanti-corrosion property and the corner portions, concretely, portionsincluding the periphery of each of the suction valve 42, the abovedischarge valve 43, and the movable wall 44. By passing N₂ gas or thelike through this ventilation system 92, without the liquid chemicalstaying in the portion with a relatively low anti-corrosion property andthe corner portions, the liquid chemical passes through only theregulated region of the flow passage 41. Accordingly, corrosion due tothe liquid chemical or the chemical vapor can be prevented.

Next, a flow rate regulation system using the flow rate regulation means34 for regulating the flow rate of ultrapure water passing through thepiping system 23, will be described.

As shown in FIG. 1, this flow rate regulation means 34 is provided at aportion corresponding to the downstream of ultrapure water of theconnection portion of the capillary 33 of the supply flow passage 23,and regulates the flow rate of ultrapure water or a cleaning liquid byutilizing generation of a so-called Karman vortex. That is, when thereis some obstacle in a flow, Karman vortices are generated on thedownstream side, and it is known that the generation frequency of thesevortices is in proportion to the flow velocity in a wide Reynolds numberrange without being affected by temperature/pressure or the like, andthe flow rate can be measured by detecting the number of these vortices.And, the measurement result of the flow rate regulation means 34 istransmitted to the chemical supply control means 37, and opening andclosing of the flow rate control valve of the flow rate regulation means34 is controlled.

Next, a concentration regulation system using the concentrationregulation means 35—for regulating the concentration of a cleaningliquid passing through the piping system 23, will be described.

As shown in FIG. 1, this concentration regulation means 35 is providedat a portion corresponding to the downstream of the cleaning liquid ofthe connection portion of the capillary 33 of the supply flow passage23, and constructed by molding two pairs of annular solenoids(excitation transformers T1 and detection transformers T2 through whichan alternating current flows) with a resin. By dipping this in thecleaning liquid, a closed circuit that the cleaning liquid intersectseach of the two annular solenoids is formed. When a constant alternatingcurrent is made to flow in the excitation transformer T1 of one annularsolenoid, a constant magnetic field is generated in the core. Because acurrent flows in the cleaning liquid in accordance with itsconductivity, the magnetic field according to the current is generatedin the detection transformer T2 of the other annular solenoid, besides,an induced electromotive force is generated in a coil, and this inducedelectromotive force is in proportion to the conductivity of the cleaningliquid. The conductivity measured in this manner and the cleaning liquidconcentration (particularly, HF concentration) have a very highrelation, and the cleaning liquid concentration can be obtained withhigh accuracy from a calibration curve obtained beforehand. And, themeasurement result of the concentration regulation means 35 istransmitted to the concentration control means 38, and fed back to thechemical supply control means 37, and the voltage applied to thechemical supply pump 31 is regulated to perform flow rate control of thecleaning liquid.

Next, a chemical mixing system using the mixing means 36 disposed at theconnection portion to the capillary 33 of the piping system 23, forproducing a rotational flow in a cleaning liquid to stir and uniformizethe cleaning liquid, will be described.

FIGS. 22A to 22C and FIGS. 23A and 23H exemplify various forms of thismixing means 36. The mixing means 36 has a cone shape, in which aflowing-in portion 36 a to the mixing means 36 in the piping system 23and a flowing-out portion 36 b are provided with being offset slightly.When a liquid chemical is supplied from the capillary 33, a rotationalflow in a predetermined rotational direction is produced due to the coneshape of the mixing means 36 and the positional relation between theflowing-in portion 36 a and the flowing-out portion 36 b. Thereby, theliquid chemical is stirred to be uniform with ultrapure water, and flowsin the piping system 23.

Here, in FIG. 22A, the mixing means 36 of the cone shape is provided soas to be a state that the flow passage expands from the capillary 33,inversely in FIG. 22B, the cone shape is provided so as to be a statethat the flow passage contracts. Besides, in FIG. 22C, the capillary 33and the mixing means 36 are provided so as to be slightly distant.Further, in FIG. 23A, the flowing-in portion 36 a and the flowing-outportion 36 b are provided so as to be substantially perpendicular, and,in FIG. 23B, the flowing-in portion 36 a and the flowing-out portion 36b are provided so as to be inverse in flow direction.

FIGS. 24A and 24B (FIG. 24A is a cross section and FIG. 24B is avertical section) show another form of the mixing means 36. In thismixing means 36, four connecting tubes 32 and capillaries 33 areconnected symmetrically, and it has a tapered shape toward thedownstream side of the cleaning liquid. And, a spiral pitch 36 c isformed in the flow passage of its inner wall surface, and a rotationalflow is produced in the cleaning liquid to stir, by the cleaning liquidpassing through the pitch, and uniformizing is intended.

FIGS. 25A and 25B (FIG. 25A is a cross section and FIG. 25B is avertical section) show still another form of the mixing means 36. Inthis mixing means 36, four connecting tubes 32 and capillaries 33 areconnected symmetrically, a gap 36 d along the inner wall surface and atubule 36 e in the central portion form the flow passage for thecleaning liquid, and a spiral pitch 36 c is formed in part of the gap 36d.

And, in this mixing means 36, as shown in FIG. 26, the flowing-outportion 36 b has a tapered shape toward the downstream side of thecleaning liquid.

In this manner, by the mixing means 36, it becomes possible to suppressgeneration of concentration unevenness of the liquid chemical apt tooccur in the piping system 23, and to supply the cleaning liquid surelyuniformized.

Next, a system for regulating the chemical quantity of the chemicalstorage tank 21 into a predetermined value, will be described.

Here, exemplified is a case that a plurality of chemical storage tanks21 (three in the example shown in the drawing) is provided as thechemical quantity regulation system, as shown in FIG. 14. As shown inFIG. 14, in the chemical storage tanks 21, HF, H₂O₂, and a surfaceactive agent are stored in this order as liquid chemicals A, B, and C.As shown in FIG. 27, each chemical storage tank 21 (here, among three,the chemical storage tank 21 in which the liquid chemical A is stored isexemplified as a representative) is constructed by comprising a maintank 21 a in which a sufficient quantity of liquid chemical is stored,and an auxiliary tank 21 b which is connected to the main tank 21 a andonly a necessary quantity of liquid chemical is supplied to from themain tank 21 a.

In each auxiliary tank 21 b, provided is a liquid surface regulationmeans 49 for regulating the liquid surface level of the supplied liquidchemical by the pressure of N₂ gas to control the chemical quantity. Asshown in FIG. 28, this liquid surface regulation means 49 has-a pair ofbar-like sensors 49 a and 49 b made of, e.g., carbon, and obtains theliquid surface level by measuring the electrostatic capacity of theliquid-chemical between the bar-like sensors 49 a and 49 b as describedbelow.

Here, the principle of the liquid surface level measurement by theliquid surface regulation means 49, will be described. The distance fromthe liquid surface of the liquid chemical to the lower end of thebar-like sensor is L, the interval between the bar-like sensors is D,and r1, r2, a, d, and δ are defined as shown in FIG. 29. In this case,since

δ/a=a/d=r1/r2

is given, if there are the charge of +Q on the circle 1 (cross sectionof one bar-like sensor) and the charge of −Q on the circle 2 (crosssection of the other bar-like sensor), in relation to all points of onebar-like sensor,

$\begin{matrix}{{\left( {Q/L} \right)2{{\pi ɛ}_{o}\left( {{\ln \left( {r\; 1} \right)} - {\ln \left( {r\; 2} \right)}} \right)}} = {\left( {Q/L} \right)2{\pi ɛ}_{o}{\ln \left( {r\; {1/r}\; 2} \right)}}} \\{= {\left( {Q/L} \right)2{\pi ɛ}_{o}{\ln \left( {a/d} \right)}}}\end{matrix}$

is given. Since the charge Q distributing on the straight line 1-2 makesthe same electric field outside the bar-like sensor as that in case thatthe same amount of charge is present on the surface of the bar-likesensor, the potential difference between two bar-like sensors is equalto

(Q/L)π∈_(o)ln(a/d),

and the capacitance C is given by

C=π∈ _(o) L/ln(a/d)  (1).

Substituting a/d=exp(π∈_(o)L/C) for the expression (1),

$\begin{matrix}{{D/a} = {{\exp \left( {{\pi ɛ}_{o},{L/C}} \right)} + {\exp \left( {{- {\pi ɛ}_{o}}{L/C}} \right)}}} \\{= {2{\cosh \left( {{\pi ɛ}_{o}{L/C}} \right)}}}\end{matrix}$

is given, and

C=π∈ _(o) L/(cos h ⁻¹ D/2a)  (2)

is given. From this expression (2), by measuring the value of C, thevalue of L can be obtained.

In this manner, according to the liquid surface regulation means 49, bymeasuring the electric capacity of dipped portions of the bar-likesensors 49 a and 49 b in the liquid chemical and its change over time,the liquid surface level and its changing speed can be calculated. Thatis, by using the liquid surface level as a parameter, for example, thedeviation from the liquid surface level expected value is measured andregulation to the expected value can be made. By using the changingspeed of the liquid surface level as a parameter, by measuring theincrease of the above changing speed, an accident caused by it, forexample, leakage of the main tank 21 a can be checked.

Accordingly, by this liquid surface regulation means 49 it becomespossible efficiently and surely to measure the liquid surface level of aliquid chemical and its changing speed, and chemical supply at need,sure detection of generation of various troubles attendant upon chemicalsupply, etc., can be realized.

Actually, FIG. 30 shows the results that the relation between the liquidsurface level of a liquid chemical and the capacitance is examined. ThisFIG. 30 shows the relation between calculated values with the expression(2) and measured values. Here, the measured values were measured underthe conditions of ∈_(o)=7.17×10⁻¹⁰ F/m, the radius of the bar-likesensor=2 mm, the interval=10 mm, and the length of the bar-likesensor=31.0 mm, and the calculated values were calculated using the sameconditions. In this characteristic graph, the axis of abscissas givesthe liquid surface level of the liquid chemical (0 mm at full), and theaxis of ordinates gives the capacitance (nF). In this manner, thecalculated values and the measured values are almost equal, and it isfound that C and L have a proportional relation.

Next, a system for defoaming as maintenance of the chemical supplysystem, will be described.

As shown in FIG. 1, this defoaming system 101 has a connecting tube 102provided so as to branch from a portion corresponding to the upstream ofultrapure water of the connection portion to the capillary 33 of thesupply flow passage 23, and the connecting tube 102 is connected to thechemical supply pump 31 to form a closed system. And, when the chemicalstorage tank 21 is unused, a valve 103 is opened, the chemical supplypump 31 is driven, and ultrapure water is made to flow in the closedsystem to defoam.

Thereby, the chemical supply pump 31, the capillary 33, etc., areefficiently cleaned, and defoaming is surely performed.

Next, a dissolved gas removal system for suppressing bubbling ofdissolved gas in a liquid chemical in discharging, in order to aim atfurther improvement of the chemical discharge accuracy of the chemicalsupply pump 31, will be described.

The chemical supply pump 31 is a diaphragm pump repeatedly performingdischarge/suction of a liquid chemical periodically by oscillation driveof the movable wall 44 by the piezoelectric oscillator 46 that is ashaker as described above. In oscillation drive, if dissolved gasbubbles in the liquid chemical, remarkable deterioration is brought onthe flow rate characteristic of the liquid chemical, and, in the worstcase, it is apprehended that gas lock occurs and the discharged flowrate becomes zero. Because high-degree accuracy is required for thedischarge quantity and the discharge speed of the liquid chemical, theaffection of bubbling of dissolved gas on the discharged flow rate is avery important problem.

The present inventors have perceived that bubbling of dissolved gasgreatly depends on mechanical characteristics of the chemical supplypump 31 and physical characteristics (relative temperature/pressure) ofthe liquid chemical, and thought that-bubbling of dissolved gas in theliquid chemical is suppressed by controlling them. Hereinafter,dissolved gas removal systems for making those controls will bedescribed in order.

(1) Control of a Mechanical Characteristic (Oscillation Manner) of theChemical Supply Pump 31:

Normally, the oscillation manner (voltage application manner) of themovable wall 44 by the piezoelectric oscillator 46 has an oscillationwave form that draws a typical sine curve with substantially the sameperiod, as shown by a broken line in FIG. 31A. In this case, theprobability of dissolved gas bubbling in a liquid chemical is high whena pressure less than the atmospheric pressure (negative pressure) isapplied to the liquid chemical. So, in this example, by controlling suchthat the absolute value of the negative pressure when the liquidchemical is sucked, is as small as possible, and the suction time islonger than the discharge time, bubbling of dissolved gas is suppressedas few as possible.

Concretely, as shown by a solid line in FIG. 31A, in one period, therate of change of pressure at the time of suction that a negativepressure is produced, is suppressed to be gentle in comparison with thatat the time of discharge that a positive pressure is produced. Togetherwith this, as shown by the pressure application manner of FIG. 31B, theabsolute value of the negative pressure in suction is made smaller thanthe positive pressure in discharge, and this absolute value of thenegative pressure is made as small as possible. That is, the impulse(the absolute value thereof) due to the negative pressure shown by thearea with slanting lines in FIG. 31B is made smaller than the impulsedue to the positive pressure, and as small as possible unless thefunction as the chemical supply pump is detracted. By the former (FIG.31A), bubbling due to rapid pressure change at the time of suction isprevented, and, by the latter (FIG. 31B), the load on the liquidchemical due to the negative pressure is relieved to prevent bubbling.That is, by control standing on both of these, it becomes possible tosuppress bubbling of dissolved gas in the liquid chemical as minimum aspossible.

(2) Relative Temperature Control of Liquid Chemical:

Dissolution of gas into liquid chemical is in inverse proportion totemperature (Henry's law). This inverse proportion relation can be seenevenly in relation to air, nitrogen, and oxygen thinkable as dissolvedgas, as shown in FIG. 32. Accordingly, if the relative temperature tothe outside of the chemical supply pump 31 is decreased, the solubilityof dissolved gas in the liquid chemical in the flow passage 41 of thechemical supply pump 31 becomes great to suppress bubbling. So, in thisexample, a cooling means is provided to cool the chemical supply pump 31(and the piping portion connecting between the chemical tank 21 and thechemical supply pump 31).

Concretely, as shown in FIG. 33, a cooling means 111 is provided on thechemical supply-pump 31. As this cooling means 111, suitable is oneincluding a Peltier element as the principal component, one in which acooling liquid is circulated on the periphery of the chemical supplypump 31, or the like. By providing such a cooling means 111 and coolingthe chemical supply pump 31 to a predetermined temperature, it becomespossible to suppress bubbling of dissolved gas in the liquid chemical asminimum as possible.

(3) Degassing of Liquid Chemical:

If dissolved gas is degassed from a liquid chemical before the liquidchemical is sucked in the chemical supply pump 31, bubbling insuction/discharge of the chemical supply pump 31 is prevented. So, inthis example, a degassing module comprising a diaphragm tube whosesurface layer is a degassing film, is provided between the chemical tank21 and the chemical supply pump 31.

FIGS. 34A and 34B are typical views showing a diaphragm tube that is acomponent of a degassing module. Here, it is suitable to construct thediaphragm tube 112 by a porous film or a hollow film whose material isPTFE (polytetrafluoroethylene) or the like.

As shown in FIGS. 34A and 34B, by making the outside of the diaphragmtube 112 in a high-degree vacuum state, degassing is performed using thepressure difference between the inside of the tube and the outside. Byusing this degassing module, it becomes possible to suppress bubbling ofdissolved gas (air, oxygen, or nitrogen in the example shown in thedrawing) in the liquid chemical as minimum as possible.

As the dissolved gas removal system, not only (1) to (3) are usedindividually, but also they are executed in proper combination to aim atfurther sure bubbling suppression.

Among various additional systems described above, together with controlof the chemical supply pump 31, at least the mixing prevention system,the bubble/damage detection system, the cleaning liquid flow detectionsystem, the flow rate regulation system, the concentration regulationsystem, the chemical mixing system, the chemical quantity regulationsystem, the dissolved gas removal system, etc., are driven by therespective control means of the control system 26.

Second Example

Successively, the second example of the present invention will bedescribed. In this example, like the first example, a substrate cleaningapparatus of single wafer spin cleaning type comprising a cleaningchamber and a chemical supply system, is disclosed, but it differs onthe point that the construction of the chemical supply apparatus of thechemical supply system is different. The same components or the like asthose of the substrate cleaning apparatus of the first example aredenoted by the same references, and their explanations will be omitted.

FIG. 35 is a schematic sectional view showing the whole construction ofthe substrate cleaning apparatus of this example.

The substrate cleaning apparatus of this example is constructed bycomprising a cleaning chamber 1 and a chemical supply system 2. Here,the chemical supply system 2 is constructed by comprising a chemicalstorage tank 21, a chemical supply apparatus 121 connected to thechemical storage tank 21 for positively performing chemical supply, apiping system 23 connected to the chemical supply apparatus 121 to forma supply flow passage that is a passage for ultrapure water with which aliquid chemical is mixed, a pair of discharge nozzles 24 and 25 forsupplying a cleaning liquid to the surfaces of a wafer 11 set in thecleaning chamber 1, and a control system 26 for regulating variousconditions such as the concentration and the flow rate of the cleaningliquid supplied from the discharge nozzles 24 and 25.

The chemical supply apparatus 121 is constructed by comprising a firstpump 122 for sucking a liquid chemical from the chemical storage tank 21to feed out, a second pump 123 of force feed type for storing the liquidchemical fed out from the first pump 122, applying a predeterminedpressure to the liquid chemical, and supplying a predetermined quantityof liquid chemical by controlling opening and closing of a valve 145, aconnecting tube 32 connecting the piping system 23 and the second pump123 to form a connecting flow passage, and a capillary 33 directlyconnecting to the supply flow passage of the piping system 23 in theconnecting tube 32.

The first pump 122 may be a diaphragm pump like the chemical supply pump31 or a pump of another construction if the predetermined quantity ofliquid chemical is accurately supplied from the chemical storage tank 21to the second pump 123.

The second pump 123 is a pump of force feed type_, and is constructed bycomprising a pressurized vessel 131 that is a chemical storage means inwhich the liquid chemical supplied from the first pump 122 is stored, apressure control means 132 for making pressure control by feeding, e.g.,N₂ gas into the liquid chemical in the chemical storage means 131, and aliquid level measurement means 133 for measuring change in liquidquantity of the liquid chemical in the pressurized vessel 131.

The pressurized vessel 131 is made of PTFE at the inner wall 143 and ametal at the outer wall 144, and a flowing-in port 141 to which theliquid chemical from the first pump 122 is supplied, and a flowing-outport 142 to discharge the liquid chemical toward the connecting tube 32,are connected.

The pressure control means 132 has an auto pressure control (APC) valveautomatically controlling the pressure to the liquid chemical in thepressurized vessel 131, and automatically controls the supply quantityof, e.g., N_(Z) gas into the pressurized vessel 131 on the basis of acontrol signal from the control system 26.

The liquid level measurement means 133 has a pair of bar-like sensors133 a and 133 b made of conductive members of, e.g., carbon or the like,and obtains the liquid surface level (and the change quantity thereof)by measuring the electrostatic capacity of the liquid chemical betweenthe bar-like sensors 133 a and 133 b. The measurement principle of theliquid level measurement means 133 is the same as the case using thebar-like sensors 49 a and 49 b of the liquid surface regulation means 49described above, and, by measuring the electrostatic capacity of thedipped portions of the bar-like sensors 133 a and 133 b in the liquidchemical and its change over time, the liquid surface level and thechanging speed thereof are calculated. The result measured by thisliquid level measurement means 133 is fed back to the control system 26,and, on the basis of this, a predetermined control signal is sent out tothe pressure control means 132.

Here, the operation principle of the second pump 123 will be described.

When the pressure control means 132 receives the control signal, apredetermined quantity of N₂ gas is fed into the pressurized vessel 131,and thereby a pressure P₁ is applied to the liquid chemical in thepressurized vessel 131. At this time, when the pressure of ultrapurewater passing through the piping system 23 is P₀, a predeterminedquantity of liquid chemical is discharged from the flowing-out port 142due to the pressure difference (P₁−P₀). When the flow rate of the liquidchemical in the capillary 33 is Q, the flow rate Q is expressed with thepressure difference (P₁−P₀) and a coefficient k depending on the shapeof the capillary 33 into:

Qαk(P₁−P₀)^(1/2)  (3).

For example, when the pressure P₀ is 1.5 kg/cm² and the pressure P₁ is3.0 kg/cm², the flow rate Q corresponding to the pressure difference(P₁−P₀) is determined by the expression (3).

The control system 26 comprises a chemical supply control means 37 forregulating the supply quantity of the liquid chemical from the chemicalstorage tank 21 to the pressurized vessel 131 by the first pump 122,regulating the supply quantity of the liquid chemical to ultrapure waterby the second pump 123, and further driving a flow rate regulation means34, and a concentration control means 38 for driving a concentrationregulation means 35.

Here, the chemical supply control means 37 controls the-opening andclosing timing of the valve 145 in addition to the pressure controlmeans 132 and the liquid level measurement means 133 as described abovewhen it controls drive of the second pump 123, and regulates thedischarge time of the liquid chemical to the connecting tube 32 and stopof discharge.

And, in the control system 26, the chemical supply control means 37 andthe concentration control means 38 are connected, the result ofconcentration control by the concentration control means 38 is fed backto the chemical supply control means 37 to control the first and secondpumps 122 and 123, and the supply quantity of the liquid chemical isregulated.

Also in the substrate cleaning apparatus of this example, like the caseof the first example, in order to ensure the further suppression ofparticle generation or the like and the accuracy of the chemicalconcentration of the cleaning liquid, various additional systems areprovided to the chemical supply system constructed as described above.Concretely, like the first example, listed are a mixing preventionsystem, a bubble/damage detection system, a cleaning liquid flowdetection system, a corrosion prevention system, a flow rate regulationsystem, a concentration regulation system, a chemical mixing system, achemical quantity regulation system, a defoaming system, a dissolved gasremoval system, etc. Control of these additional systems is also made bythe control system 26.

In this manner, in the substrate cleaning apparatus of this example, bythe first and second pumps 122 and 123, the liquid chemical isdischarged by drive control of the pressure control means 132, and itbecomes possible to discharge and supply a desired quantity of liquidchemical with accuracy.

Further in this example, provided is the chemical supply apparatus 121including these first and second pumps 122 and 123 as components. Thischemical supply apparatus 121 mixes the liquid chemical from thecapillary 33 with ultrapure water passing through the piping system 23by drive of the first and second pumps 122 and 123, and mixturesolutions (cleaning liquids) at various concentrations can easily becompounded at need. Here, in case that the discharge direction of theliquid chemical is a direction substantially perpendicular to the flowdirection of ultrapure water, by applying a pressure to the liquidchemical such that the linear velocity of the liquid chemical dischargedfrom the tubule member is sufficiently larger than the linear velocityof ultrapure water passing through the piping system 23, the liquidchemical reaches the opposite wall surface of the piping system 23 inultrapure water, and a mixture solution at a uniform concentration iscompounded in a moment.

Further in this example, provided is the chemical supply system 2including the chemical supply apparatus 121 as a component and forsupplying a cleaning liquid. In this chemical supply system 2, becauseit is possible to produce cleaning liquids at desired concentrations atneed as described above, enough is the easily movable small-sizedreservoir 21 of the liquid chemical that is the formulated concentrate.That is, in this chemical supply system 2, there is no necessity ofproviding very large reservoirs for mixture solutions different inchemical concentration and kind as conventionally, and not only particlemixing to a cleaning liquid, or the like, can be suppressed, but alsoremarkable reduction/simplification of the scale of the whole system canbe realized. Accordingly, in the substrate cleaning apparatus of thisexample provided with this chemical supply system 2, it becomes possiblerapidly and easily to supply various pure cleaning liquids different inconcentration and kind.

The present invention is not limited to these examples. For example, thechemical supply system is applicable to not only the substrate cleaningapparatus but also any other apparatus in which large quantities ofliquid chemicals of various kinds and concentrations are necessary.

1. A chemical supply apparatus comprising: a chemical supply pump, and aconnecting flow passage connecting a supply flow passage that is apassage for a solvent with which said liquid chemical is mixed, and saidchemical supply pump, wherein a tubule member directly connecting saidsupply flow passage is provided in said connecting flow passage, and, insaid chemical supply pump, a flow passage for passing a predeterminedliquid chemical is formed, a suction valve which is closed by pressurerise of said liquid chemical is provided at a flowing-in port of saidflow passage, and a discharge valve which is closed by pressure fall ofsaid liquid chemical is provided at a flowing-out port of said flowpassage, at least part of a liquid contact surface in said flow passageis made of a compact member with non-permeability and a highanti-corrosion property to said liquid chemical, and part of saidcompact member is made into a movable wall, a shaker connected to saidmovable wall is provided, and said movable wall is oscillated in adirection substantially perpendicular to its wall surface by drive ofsaid shaker to change the volume of said flow passage periodically, and,by drive of said chemical supply pump, said liquid chemical isdischarged from said tubule member into said solvent passing throughsaid supply flow passage to compound a mixture solution at a desiredconcentration.
 2. A chemical supply apparatus as claimed in claim 1,wherein the discharge direction of said liquid chemical is a directionsubstantially perpendicular to the flow direction of said solvent, andsaid chemical supply pump gives said liquid chemical a pressure suchthat the linear velocity of said liquid chemical discharged from saidtubule member is greater than the linear velocity of said solventpassing through said supply flow passage.
 3. A chemical supply apparatusas claimed in claim 1, wherein an electrode surrounding part of saidconnecting flow passage is provided, and the electrostatic capacity ofsaid liquid chemical passing through said connecting flow passage ismeasured by said electrode.
 4. A chemical supply apparatus as claimed inclaim 1, comprising a chemical discharge stop means surrounding part ofsaid connecting flow passage near said tubule member, said chemicaldischarge stop means operating so as to suck some quantity of saidsolvent in said supply flow passage from said tubule membersynchronously with stoppage of said chemical supply pump.
 5. A chemicalsupply apparatus as claimed in claim 4, wherein said chemical dischargestop means has an electric heating system for heating said liquidchemical to a predetermined temperature, and heating by said electricheating system is stopped synchronously with stoppage of said chemicalsupply pump.
 6. A chemical supply apparatus as claimed in claim 4,wherein said chemical discharge stop means has a compression system, anddrives synchronously with stoppage of said chemical supply pump.
 7. Achemical supply apparatus as claimed in claim 1, comprising a chemicaldischarge stop means which is directly connected to part of saidconnecting flow passage near said tubule member, and comprises anothertubule member connected to a portion corresponding to the upstream ofsaid solvent of the connection portion of said tubule member of saidsupply flow passage, said chemical discharge stop means operating so asto supply said solvent from said other tubule member into said supplyflow passage synchronously with stoppage of said chemical supply pump,and to push out said liquid chemical remaining in said connecting flowpassage to said supply flow passage side by an action of a check valveprovided on said chemical supply pump side.
 8. A chemical supplyapparatus as claimed in claim 7, wherein a check valve is provided nearan inlet of said other tubule member, and the concentration change ofsaid liquid chemical is minimized.
 9. A chemical supply apparatus asclaimed in claim 1, wherein said tubule member has an electric heatingsystem for heating said liquid chemical to a predetermined temperature,and heating by said electric heating system is stopped synchronouslywith stoppage of said chemical supply pump to suck some quantity of saidsolvent in said supply flow passage.
 10. A chemical supply apparatus asclaimed in claim 1, wherein a pair of temperature detection elements isembedded near the connection portion to said supply flow passage of saidtubule member, and the temperature difference between said temperaturedetection elements is detected synchronously with said chemical supplypump, and the flow condition of said mixture solution is monitored. 11.A chemical supply apparatus as claimed in claim 1, wherein said solventis ultrapure water.
 12. A chemical supply apparatus as claimed in claim1, wherein said tubule member is conductive.
 13. A chemical supplyapparatus as claimed in claim 12, wherein said tubule member is made ofamorphous carbon.
 14. A chemical supply system comprising: at least onekind of easily moveable chemical reservoir, a chemical supply apparatusconnected in correspondence to said chemical reservoir, and said supplyflow passage, said chemical supply apparatus comprising: a chemicalsupply pump, and a connecting flow passage connecting the supply flowpassage that is a passage for a solvent with which said liquid chemicalis mixed, and said chemical supply pump, wherein a tubule memberdirectly connected to said supply flow passage is provided in saidconnecting flow passage, and, in said chemical supply pump, a flowpassage for passing a predetermined liquid chemical is formed, a suctionvalve which is closed by pressure rise of said liquid chemical isprovided at a flowing-in port of said flow passage, and a dischargevalve which is closed by pressure fall of said liquid chemical isprovided at a flowing-out port of said flow passage, at least part of aliquid contact surface in said flow passage is made of a compact memberwith non-permeability and a high anti-corrosion property to said liquidchemical, and part of said compact member is made into a movable wall,and a shaker connected to said movable wall is provided, and saidmovable wall is oscillated in a direction substantially perpendicular toits wall surface by drive of said shaker to change the volume of saidflow passage periodically, said chemical supply apparatus dischargingsaid liquid chemical from said tubule member into said solvent passingthrough said supply flow passage by drive of said chemical supply pumpto compound a mixture solution at a desired concentration, said chemicalsupply system being characterized by discharging said mixture solutionmade into the predetermined concentration from a discharge portionprovided at an end portion of said supply flow passage, by drive of saidchemical supply pump of said chemical supply apparatus.
 15. A chemicalsupply system as claimed in claim 14, comprising a control system forregulating said mixture solution supplied from said discharge portion.16. A chemical supply system described in claim 15, comprising: a flowrate regulation means for regulating the flow rate of said solvent orsaid liquid chemical passing through said supply flow passage, and aconcentration regulation means for regulating the concentration of saidmixture solution passing through said supply flow passage, wherein saidcontrol system has a chemical supply control means for regulating thesupply quantity of said liquid chemical to said solvent of said chemicalsupply pump, and a concentration control means for driving saidconcentration regulation means, said chemical supply control meansdrives said flow rate regulation means, said chemical supply controlmeans and said concentration control means are connected, and a resultof concentration control by said concentration control means is fed backto said chemical supply control means to regulate the supply quantity ofsaid liquid chemical.
 17. A chemical supply system as claimed in claim14, comprising a mixing means for producing a rotational flow in saidmixture solution to stir and uniformize said mixture solution, whereinsaid mixing means has a spiral pitch in a flow passage for said mixturesolution, and a rotational flow is produced by said mixture solutionpassing through said pitch.
 18. A chemical supply system as claimed inclaim 14, comprising a mixing means for producing a rotational flow insaid mixture solution to stir and uniformize said mixture solution,wherein, in said mixing means, a flowing-in portion to said mixing meansin said supply flow passage and a flowing-out portion are provided to beslightly offset.
 19. A chemical supply system as claimed in claim 14,characterized in that said chemical reservoir is constructed by having amain reservoir in which a sufficient quantity of said liquid chemical isstored, and an auxiliary reservoir which is connected to said mainreservoir and only a necessary quantity of said liquid chemical issupplied to from said main reservoir, and said auxiliary reservoir has aliquid surface level regulation means for regulating the liquid surfacelevel of said liquid chemical supplied to control said chemicalquantity.
 20. A chemical supply system as claimed in claim 19, whereinsaid liquid surface level regulation means is a pair of bar-like sensorsmade of conductive members, and calculates said liquid surface level andthe changing speed thereof by measuring the electrostatic capacity ofthe dipped portions of said bar-like sensors in the liquid chemical andits change over time.
 21. A chemical supply system as claimed in claim14, wherein said supply flow passage has a connecting tube branchingfrom a portion corresponding to the upstream of said solvent of theconnection portion to said tubule member, said connecting tube isconnected to said chemical supply pump to form a closed system, and,when said chemical reservoir is unused, said solvent is made to flow insaid closed system to defoam.
 22. A chemical supply system as claimed inclaim 14, wherein a plurality of said chemical supply apparatus isconnected to said chemical reservoirs in correspondence to a pluralityof said chemical reservoirs in each of which a predetermined: Liquidchemical is stored, and said chemical supply apparatus are arbitrarilydriven to mix said liquid chemicals with said solvent passing throughsaid supply flow passage, in a desired order.
 23. A chemical supplysystem as claimed in claim 14, wherein a degassing tube whose surfacelayer is a degassing film is provided between said chemical reservoirand said chemical supply pump, said liquid chemical is passed throughsaid degassing tube in a state that the external temperature pressure ofsaid degassing tube is low, and degassing of said liquid chemical isperformed.